1. Field of the Invention
The present invention relates to a method and an apparatus for automatic steering control of an automobile capable of driving under an automatic steering mode.
2. Description of the Background Art
An automatic steering control of an automobile has been achieved conventionally by detecting a white line drawn on a road and controlling the steering of the automobile automatically such that the automobile follows this white line, in a manner shown in FIG. 1.
Namely, in this conventional method of automatic steering control shown in FIG. 1, a distance AA' from a point A located on a view axis AX of a camera CA provided on an automobile 100 with an orientation along a direction of a car central axis to a point A' located on a white line SW drawn on a road at which a line SA perpendicular to the view axis AX at the point A intersects with the white line SW is calculated, and a steering angle is calculated according to the calculated distance AA'. Here, the steering angle .phi. is calculated by using a so called regression equation for determining a steering angle .phi. from three distances AA' (i-2), AA' (i-1), and AA' (i) which are successively sampled at successive sampling timings i-2, i-1, and i, according to the following equation (1). EQU .phi.=a.sub.i AA'(i)+a.sub.i-1 AA'(i-1)+a.sub.i-2 AA'(i-2)+a.sub..phi.( 1)
where, a.sub.i, a.sub.i-1, a.sub.i-2, and a.sub..phi. are constants. Now, in order to widen the scope of the camera view, the camera CA can be switched to another camera CB provided on the automobile 100 with an orientation along a direction inclined by an angle .theta. from the car central axis toward a front side of the automobile 100. In such a case, a distance BB' from a point B located on a view axis BX of the camera CB to a point B' located on the white line SW drawn on a road at which a line SB perpendicular to the view axis BX at the point B intersects with the white line SW is calculated, and a steering angle is calculated according to the calculated distance BB' by using the regression equation for the camera CB which has a form similar to that of the above equation (1) for the camera CA.
In this type of a conventional automatic steering control method using a plurality of cameras oriented in different directions which are sequentially switched in order to obtain a wider scope of the camera view, it has been necessary to provide as many numbers of regression equations as a number of the cameras involved, which made this type of method clumsy.
Also, there has been a problem that when a plurality of cameras were replaced by a single camera capable of changing its own orientation by being rotated, it becomes necessary to provide infinitely many regression equations, which is impractical.